C# 4 and .NET 4

system.Transactions ❘ 611
}
}
}
}
finally
{
connection.Close();
}
A big advantage of creating transactions with System.EnterpriseServices is that multiple objects can
easily run within the same transaction, and transactions are automatically enlisted. The disadvantages are
that it requires the COM+ hosting model, and the class using the features of this technology must be derived
from the base class ServicedComponent .
Enterprise Services and using COM+ transactional services are covered in the
downloadable Chapter 51, “Enterprise Services.”
sysTem.TransaCTions
The namespace System.Transactions became available with .NET 2.0 and brings a modern transaction
programming model to .NET applications.
This namespace offers a few dependent TransactionXXX classes. Transaction is the base class of all
transaction classes and defi nes properties, methods, and events available with all transaction classes.
CommittableTransaction is the only transaction class that supports committing. This class has a
Commit() method; all other transaction classes can do only a rollback. The class DependentTransaction is
used with transactions that are dependent on another transaction. A dependent transaction can depend on a
transaction created from the committable transaction. Then the dependent transaction adds to the outcome
of the committable transaction whether or not it is successful. The class SubordinateTransaction is used
in conjunction with the Distributed Transaction Coordinator (DTC). This class represents a transaction that
is not a root transaction but can be managed by the DTC.
The following table describes the properties and methods of the Transaction class.
TransaCTion Class member
Current
IsolationLevel
TransactionInformation
EnlistVolatile()
EnlistDurable()
EnlistPromotableSinglePhase()
Rollback()
desCriPTion
The property Current is a static property without the need to have
an instance. Transaction.Current returns an ambient transaction
if one exists. Ambient transactions are discussed later in this chapter.
The IsolationLevel property returns an object of type
IsolationLevel. IsolationLevel is an enumeration that defi nes
what access other transactions have to the interim results of the
transaction. This affects the I in ACID; not all transactions are isolated.
The TransactionInformation property returns a
TransactionInformation object. TransactionInformation
gives you information about the current state of the transaction, the
time when the transaction was created, and transaction identifi ers.
With the enlist methods EnlistVolatile(), EnlistDurable(),
and EnlistPromotableSinglePhase(), you can enlist custom
resource managers that participate with the transaction.
With the Rollback() method, you can abort a transaction and undo
everything to set all results to the state before the transaction.
continues
www.it-ebooks.info